Determination Foreign Object Detection Area in Electric Vehicle Wireless Charging System Based on Thermal Temperature Rise Characteristic

For electric vehicle wireless charging (EVWC) systems, the foreign metal objects in the charging area will be heated, and it carries danger to the system because of the induced eddy current. Existing foreign object detection (FOD) methods focus on the same detection area as the transmitter. However, the foreign objects in the edge area of the transmitter may also be heated and cannot be detected. This paper proposes a method that can determine the area of FOD based on the temperature rise. Firstly, the loss model and the temperature variation of the foreign object is established. Secondly, the threshold of the flux density exposed to the foreign object is calculated according to the temperature rise. Then, the reasonable area of FOD can be determined by the threshold. Finally, an 11 kW EVWC prototype is set up. The experimental results prove that for a transmitter with an area of 650mm×510mm, the foreign objects in the detection area of 726mm×596mm will be heated to the dangerous temperature so the detection area needs to be extended.